Question: If $2a + 4b + c = -7$ and $2x + 8y = -9$, what is $-56y - 14x - 5c - 20b - 10a$ ?
Explanation: $= -10a - 20b - 5c - 14x - 56y$ $= (-5) \cdot (2a + 4b + c) + (-7) \cdot (2x + 8y)$ $= (-5) \cdot (-7) + (-7) \cdot (-9)$ $= 35 + 63$ $= 98$